CuNCs assisted by carbon dots to construct Z-type heterostructures: Ultra-high photocatalytic performance and peroxidase-like activity

Abstract

Copper nanoclusters (CuNCs), as novel energy level tunable photocatalysts, have been utilized to combine with various conventional inorganic catalysts to improve catalytic performance. However, conventional photocatalysts generally have fixed energy levels, which are not conducive to bi-directional adjustment of the composite catalyst energy level structure. In this work, CuNCs protected by 3-mercaptopropionic acid (CuNCs@3-MPA) and energy-level controllable carbon dots (CDs) are combined to prepare intelligent photocatalytic materials through electrostatic self-assembly strategy, i.e., CuNCs@3-MPA/CDs. The self-assembled CuNCs@3-MPA have a large specific surface area, and the Z-type heterostructure can be constructed by introducing energy-matched CDs, which can achieve the effective separation of photogenerated electron-hole pairs and directional generation of ·O2− at the same time, enabling the degradation of 98.5 % Methyl Orange (MO, 20 mg/L) in 7 min. The catalytic rate constant is increased to 0.501 min−1, which is equivalent to 3.6 times that of CuNCs@3-MPA alone. Since CuNCs@3-MPA/CDs with rich Cu(I) can perform Fenton-like reaction to catalyze the production of ·OH from H2O2, we use TMB and H2O2 as substrates to probe its peroxidase-like activity. The Km is 0.18 mM when the substrate is TMB, which is lower than that of horseradish peroxidase (HRP) (Km = 0.434 mM), indicating that the affinity between CuNCs@3-MPA/CDs and TMB is higher than that of HRP, which has a high peroxidase-like activity.